Introduction Breast cancer is one of the most common malignant tumors in women, and its incidence is increasing year by year, and the incidence is getting younger. To date, primary prevention of breast cancer is not possible, therefore, strengthening secondary prevention, early detection, early diagnosis and early treatment are crucial to reduce the death rate and improve the survival rate of breast cancer. Typical breast cancer can be manifested as a single painless lump that can be touched in the breast with fuzzy edges and little activity, and some of them can be manifested as nipple overflow, nipple invagination and orange peel-like changes in the skin. However, what we are discussing today is a kind of breast cancer that lacks the above clinical manifestations, but only has enlarged lymph nodes in the axilla as the main symptom, but no lump can be felt in the breast, which is called “occult breast cancer”. Some scholars believe that the onset of occult breast cancer may be due to the early stage of breast cancer, when the immunity of the body is strengthened, which effectively inhibits the growth of the primary tumor, but cannot effectively control the metastasis of lymphatic vessels and causes the growth of cancer foci in the axillary lymph nodes. About 2/3 of the primary foci can be found after mastectomy, ranging in size from a few millimeters to several centimeters, with an average diameter of about 1.0-1.5 cm. Screening tools Occult breast cancer is not only difficult to detect clinically, leading experienced surgeons to sometimes overlook this diagnosis, but also the positive rate of conventional objective screening tools is not promising. The rate of positivity of common diagnostic tools, such as estrogen receptor (ER) assay, is only about 50%, and the detection rate of our most common mammogram is only 5%, making it difficult to find evidence of calcification that could suggest a diagnosis. For the time being, magnetic resonance imaging (MRI) may be an effective means of diagnosing the disease, as it is not affected by the density of the breast gland and can detect microscopic lesions less than 1 cm in diameter, but its specificity is low, it is relatively expensive, and it cannot be used as a screening tool in clinical practice. CT is not suitable for breast examination because of its low accuracy in detecting calcified foci and identifying cystic disease, high examination cost, and side effects of contrast agents; while PET-CT, as an emerging examination tool in recent years, can detect foci through biomolecular metabolic activities and identify metastatic tumors in other parts of the body, which has high clinical value, but due to its limitations, some of the examination results have false positives and false negatives, and the price is more than 10,000, so the clinical applicability is also greatly limited. Although it is still difficult to diagnose occult breast cancer, once a patient develops unexplained axillary lymph node enlargement, it is recommended to consult a doctor promptly and, if necessary, to perform lymph node biopsy, estrogen receptor ER on the biopsy tissue, mammography or MRI, and to examine the whole body to exclude lymphoma, lung cancer, gastric cancer, colon cancer and ovarian cancer metastasis. Possible. Since occult breast cancer is still a relatively rare disease, there is still a lack of international clinical research on the standard of diagnosis and treatment, and there is still a great controversy between radical breast cancer surgery and axillary lymph node dissection in terms of survival and recurrence rate. Of course, since more than 70% of axillary lymph nodes enlargement are still benign lesions, we suggest that once clinical symptoms are present, there is no need to be overly alarmed and one should go to a regular hospital in time to seek a clear diagnosis and choose a personalized treatment plan suitable for oneself.